There are various types of medical dispensers, such as packages or devices for dispensing tablets, salves or inhalable substances, to mention a few. Some dispensers are provided with one or more sealed compartments containing medicament. Such compartments may take the form of blisters, pockets or a cavities-containing strip joined to a sealing strip or other suitable forms.
Taking medical dispensers in the form of inhalers, there are different types available on the market. A pressurized Metered Dose Inhaler (pMDI) releases a fixed dose of substance in aerosol form. A powder inhaler generally releases a dose of powdered substance entrained in an air stream. In a powder inhaler the powder may be provided in a bulk container of the inhaler from which doses of powder are metered for dispensing. As an alternative to a bulk container, powder inhalers may comprise a single compartment or a plurality of compartments for containing one or more discrete doses of powdered substance.
Powder inhalers comprising a plurality of compartments containing discrete doses of powdered substance, generally comprise some kind of indexing mechanism for moving the compartments sequentially into position for inhalation and also some kind of opening mechanism for accessing the substance contained in the compartments. Although some inhalers allow a short backward indexing to occur, i.e. move the compartments in a direction opposite to the normal use direction, it may be undesirable in combination with certain types of opening mechanisms, e.g. due to risk of components interfering. The normal forward indexing in an inhaler may usually be triggered by some kind of actuator, such as a lever or an outlet cover, which, when moved, causes the compartments to move. If the actuator is moved only a part of the distance, there is a risk of “half indexing”, i.e. the compartments do not move the intended distance in full. This in turn may lead to incorrect dose administration. Apart from being present in inhalers, these drawbacks of backward indexing and half-indexing could also be present in other types of medical dispensers. It would be desirable to provide a medical dispenser and an indexing method which can avoid backward indexing and/or half-indexing.